This invention relates to a monitoring apparatus associated with a fiber processing textile machine, such as a carding machine or a roller card unit in which, adjacent to and oriented toward the circumferential surface of a clothed roll or cylinder of the machine, a device for illuminating a surface area of the roll and a camera, such as a light measuring assembly having at least one CCD element are provided. An evaluating device is connected to the camera for evaluating the local light intensity changes of the image generated by the motion of the roll.
In a known apparatus of the above-outlined type, as disclosed, for example, in Published European Application 0 331 039, the fiber layer on the doffer of a carding machine is optically scanned for detecting neps. For this purpose several sensor groups are distributed along the doffer length. Each sensor group scans the fiber layer along an approximately 2.5 cm wide path. The detector groups may move transversely slowly back and forth with an amplitude that corresponds to the path width.
It is a disadvantage of the above-outlined prior art construction that providing a plurality of the sensor groups over the roll length involves a significant constructional outlay. It is a further disadvantage of the conventional arrangement that only a statistical distribution of neps in the fiber layer may be determined since the fiber layer continuously runs at high speeds in the rotary direction of the roll and moves onto the successive roll. The clothing facing the light measuring device is entirely covered by the non-uniformly thick fiber layer; it is only the points of the clothing teeth that may be recognized. The detection of the entire clothing teeth and a detection of the complete roll clothing is not intended by the conventional apparatus and such a complete detection is also not feasible thereby. The purpose of detecting the nep frequency is to draw conclusions concerning machine conditions, for example, the wear of the carding clothing. Thus, conclusions concerning the clothing are drawn indirectly from the number of neps.